Molecular seal



Jan. v26, 1965 J. c. KYLE 3,167,320

MOLECULAR SEAL Filed Jan. 25, 1961 United States Patent O 3,167,320MLECULAR SEAL James C. Kyle, Glendora, Calif., assignor to PhysicalSciences Corporation, Pasadena, Calif., a corporation of CaliforniaFiled dan. 23, 1961, Ser. No. 84,228 2 Claims. (Cl. 277-1) Thisinvention relates to a method of and means for efiecting a seal at ajuncture `between two metal parts. While the invention is widelyapplicable for static seals in general, it has been initially reduced topractice as a coupling seal and, more particularly, as la seal forr anelectrical connector for use in a high temperature environment.

The invention has specialvutility in an electrical connector for amissile wherein the coupling is exposed to the ehcects of highlycorrosive fuel under high temperature conditions. @ne fuel, for example,subjects such a connector to a gaseous compound that forms nitric acid,and nitric acid inside the electrical conductor soon creates a short inthe wiring.

The invention is based on the nding that molecular attraction becomeseffective between two metals if the two metals are brought suihcientlyclose together, and the further linding that when two metals aremaintained in such close contact progressive fusion occurs between thetwo metals. It is possible to utilize such molecular attraction andmutual fusion to make a huid-tight seal between two metals. The requiredintimate metal-to-metal contact can be obtained, however, only by theapplication of exceedingly high pressure per unit area and even thensealing can be hindered by oxides and other contaminants.

The problem is to apply these findings to the creation of a fluid-tightseal in a coupling such as a small electrical connector. Morespeciiically, the problem is to provide for the application of therequired high unit pressure Ibetween a sealing ring and two cooperatingcoupling parts of the connector and to avoid the presence of excessiveoxides or other foreign material at the metal interfaces.

This problem is solved, iirst, by using a sealing ring coniigurationthat minimizes the Contact areas and thus maximizes the unit pressureand, second, by selecting a metal for the sealing ring that is capableof considerable permanent deformation in solid state. Plasticity of thesealing ring is required in the sense of relatively high malleability,i.e., relatively high capability for permanent strain under compressionbefore fracture occurs. The deformation or plastic flow of the metal ofthe sealing ring under high pressure dislodges oxides and contaminantssuiiiciently to bring fresh, clean metal surfaces together under thepressure and the plastic flow additionally causes useful transfer of themetal of the sealing ring to each of the two cooperating connectorparts, the metal being transferred largely by a wiping action.

To carry out this concept, the sealing ring is made of malleable metaland is shaped to provide one or more narrow concentric ribs of taperedcross section on each of its sealing faces for pressure Contact with thecooperating connector parts. In the selected embodiment of theinvention, three concentric grooves are provided in each face of thesealing ring to form four narrow ribs of tapered cross section. With thecontact area of each face of the sealing ring drastically reduced inthis manner, the usual or normal pressure that is developed in thescrew-thread tightening of the coupling or connector is adequate tocause the required plastic ilow and the consequent eiectirn7 of afluid-tight seal at each o the two opposite faces of the sealing ring.

The invention has special utility for use between two 3,153,320 PatentedJan. 26, 1965 coupling parts that screw directly together because itutilizes the relative rotation that occurs at the sealing ring. Asheretofore stated, the wiping action involved in the plastic iiow of thesealing ring metal promotes transfer of the sealing ring metal to theabutting coupling parts, and the further rotary wiping action caused byscrewing the coupling parts tightly together greatly increases thewiping action and the consequent desired transfer of the metal.

The importance of grooving the sealing ring to form the narrow ribs maybe appreciated when it is considered that a tremendous pressureunattainable in practice would be required to obtain the same kind ofmolecular seal if the full area of the sealing ring were utilized. Theformation of narrow sealing ring ribs reduces the required amount ofenergy to the amount of energy that is available in the simple screwtightening of a coupling or connector in a normal manner.

Once a coupling using the ribbed sealing ring is well tightened, itholds the sealing ring under pressure to cause further plastic ow of thesealing ring metal and the inherent resiliency of the threaded couplingparts maintains the pressure even though the sealing ring yields to somedegree. This continued plastic iiow under pressure slightly increasesthe Contact areas for effective mutual molecular attraction, and thecontinued pressure promotes mutual fusion of the metals in the arcas ofcontact. Thus the effectiveness of the seal increases for a period oftime after a coupling is assembled.

It has been found that the ribbed sealing ring functions eiiectivelyeven in a coupling which is tightened without relative rotation of thecoupling parts at the sealing ring. In the assembly of such a couplingthe sealing ring is subjected solely to compression, but sufiiicentradially outward and radially inward plastic flow occurs and sufr'icientdelayed fusion of the metal occurs to make the coupling-jointfluid-tight.

The features and advantages of the invention may be understood from thefollowing detailed description and the accompanying drawing.

In the drawing, which is to be regarded as merely illustrative:

FIG. l is a fragmentary longitudinal sectional view of an electricalconnector incorporating a selected embodiment of the sealing ring;

FIG. 2 is a greatly enlarged radial section of the sealing ring inassembled position prior to the screw threaded tightening of theconnector;

FiG. 3 is a View similar to FIG. 2 showing the deformation or" thesealing ring that is created by the tightening of the connector;

FIG. 4 is a fragmentary end elevation of a tubular connector part thathas been in pressure contact with a ribbed sealing ring over a period oftime, the View showing how concentric rings of metal are transferredfrom the ribs ot the sealing ring to the surface of the connector part;

IFIG. 5 is a fragmentary sectional View of another type oi connector inwhich a ilanged nut is employed to draw the two connector parts togetherwithout the necessity of relative rotation between the two couplingparts, the parts being shown before the nut is tightened;

HG. 6 is an enlarged fragmentary sectional view of a portion of FTG. 5showing how the initial tightening of the ynut causes initial plasticiiow of the metal of the ribs of the sealing ring; and

FIG. 7 is a View similar to FEC. 6 showing how the continued pressure onthe sealing ring created by the resiliency of the coupling parts causesdelayed plastic iiow.

To illustrate a practice of the invention, FTG. l Shows a portion of anelectrical connector of a conventional type wherein two tubularconnector members comprising a plug itl and an adapter sleeve 1.2 havecorrespondingv screw threads'll and t5 by means of which the two partsscrew together. The tubular plug ltl'carries a pair of usual socketmembers l for mating with corresponding pins of a complementaryelectrical connector, the socket members being mounted in a plastic body1S and extending through plastic sleeves 2t?. The base ends of thesocket members lo are intended to 'oe welded or otherwise connected to acorresponding pair of electrical conductors (not shown) ofa cable.

The described connector construction provides a joint between the plug1t) and the adapter sleeve 20 with two confronting annular joint facesor surfaces, namely, an annular joint surface 22 of the plug and anannular joint surface 24 of the adapter sleeve. The metals of the plugylil and the adapter sleeve 12 are corrosion resistant metals,

in this instance being stainless steel, and the problem solved by theinvention is to provide a fluid-tight seal between the two confrontingjointsurfaces ZZ'and 2d that will also effectively resist corrosion. Forthis purpose, the invention provides a sealing ring 2S of suitablymalleable metal orof metal that is at least more malleable than themetal of the confronting joint surfaces.

The'common metals may be listed in order of decreasing malleability asfollows: gold, silver, copper and aluminum. All of these four metals arehighly Suitable for the present purpose, and platinum is also suitable.Various alloys are sutlciently malleable, including alloys containingindium, tin, bismuth and lead. Where a stainless steel sealing ring isrequired between two stainless steel parts,

Y the two parts may be made of AlSI 304L stainless steel,

and the interposed sealing ring may be made of AISI 302 stainless steelwhich is more malleable than the AISl 30a-L. Thus, in FlG. l the twoconnector members lil and l2 may be made of AISI 3Q4L stainless steeland the sealing ring 25 may be made of AlSl 302 stainless steel. Theessential Vfact is that the sealing ring be Vsufficiently malleable forthe required plastic-flow.

` ln the tightening of a joint by screw action, there is a limit tothepressure that may be developed between the joint surfaces in theprocedure of assembly.V The problem is to use the available pressure forthe creation of a molecular seal. It is contemplatedY that the metal ofthe sealing ring will be sufliciently malleable and the areas of contactof the sealing ring with the Vconfronting joint surfaces will-besufficiently reduced that the required plastic flowrwill be created bythe amount of pressure that is normally developed. The areas of contactbetween the sealing ring andthe confronting surfaces must bev greatlyreduced in comparison with theV area of the confronting surfaces inorder to develop the required high unit pressure. It is-for this purposethat each face of the sealing ring is formed with one or more annularribs that are of tapered configuration to minimize the areas of contact.

ln this particular practice of the invention, the relatively malleablernetal sealing ring 25 is formed on each of its opposite faces with a?Vplurality of three annular grooves. The annular grooves are flared inthe sense that their side walls are divergent as shown. lThe fourgrooves form twointermediate .annularV ribs 26 of tapered configurationas well as an inner rib ZS and outer rib 30 both ofY taperedconfiguration. in this instance, the depth of the grooves is .O inchwith the sides of the grooves at angles of 45 degrees relative to theaxis of the sealing ring. The result is that the four ribs aretriangular in cross section and are spaced apart, center to center,.010,

inch. The two sides of each of the intermediate ribs 26 are atan angleof 90 degrees relative to each other, and the'two sides of each of theinner and outer ribs 2S' and Si? are at an angle of l5 degrees from eachother.

` FGL?, shows the sealing ring positioned between the two confrontingjoint surfaces 22 and 24 prior to the tightening of the joint by screwaction. FlG. 3 shows the Y result of'tightening the joint with screwaction with the Cal consequent drawing of the two confronting jointsurfaces ZZ and towards each other to compress the sealing ring 25 andwith consequent relative rotation between the two confronting jointsurfaces.

lt can be seen in FlG. 3 that each of the narrow ribs has been truncatedby plastic flow under exceedingly high pressure per unit area. Thespreading or widening of the ribs by plastic how of tie metal of thesealing ribs in radially outward and radially inward directions underhigh unit pressure together with the scouring action created by therelative rotation at the areas of contact of the ribs brings fresh,clean metal of the sealing ring into intimate contact with fresh, cleanmetal ofthe two confronting joint surfaces under such high pressure thatmolecular attraction becomes effective to make bonds across the metalinterfaces. r

The plastic flow causes transfer of the metal of the ribs to theconfronting sealing surfaces and this transfer of metal is promoted` bythesliding action that is created by relative rotation between themetal'of the sealing ring and the metal of the confronting joint faces.This action develops such intimate contact of the metals at the metalinterfaces that molecular attraction becomes effective and fusion occursacross the metal interfaces to result in molecular bonding at theinterfaces that is highly effective for sealing in a fluid-tight manner.

The fusion across the metal interfaces is Vprogressive and continuesunder the sustained pressure long after the joint is assembled. lf sucha joint is dismantled even after only a very brief period, it will befound that the metal transferred from the ribs to each of the twoconfronting joint faces will have resulted in annular ring-shapeddeposits of the rib metal. llG. 4, for example, shows rings 32 oftransferred rib material on a joint surface 22a as observed after ajoint is dismantled. While a single annular rib may be used to effect afluid-tight seal in the above described manner, it is advantageous toprovide a plurality of annular ribs to achieve greater reliability. Thefour annular sealing ribs at each metal interface shown in HG. 3 act inseries in their sealing action so that any leakage must occur 4past allfour ribs and it is sufficient for only one rib to be completelyfluid-tight.

As heretofore stated, although the wiping action in- Y volved inrelative rotation at the metal interfaces is helpful and highlydesirable, nevertheless a sealing ring of the character described iseffective for a fluid-tight seal under pressure even when no relativerotation occurs. FlG. 5, for example, shows a joint between twocooperating members 3d and 35 which are clamped together by a nut 36. Ena well-known manner, the nut has an internal screw thread 33 inengagement with an external screw thread ed of the member 34 and has aninner radial flange 42 for engagement with an outer circumferentialshoulderV de of the second member 35. The two cooperating members 35iand 35 have respectively confronting annular joint surfaces e5 and de,and the tightening of the nut 35 draws these joint surfaces towards eachother without necessarily causing rotation between the joint surfaces.

A previously described sealing ring 25 is shown interposed between thetwo confronting joint surfaces 4:15 and de in FIG. 5 in preparation fortightening the nut. Tightening the nut causes the semng ribs to beappreciably truncated by plastic flow as indicated in FIG. 6. Undersustained pressure, the plastic flow may continue somewhat, as indicatedin HG. 7, but in any event fusion of the two metals continues across theinterface. The pressure continues even though yielding of the sealingringrnay occur after the nut is tightened, the continued pressure beingexplained by the spring action inherent in the coupling, there beingsuhicient resiliency of the metal parts for this effect.

While tightening of the nut 36 does not cause relative rotation betweenthe two members 34;*- and 3S in the joint construction shown in FIG. 5,such relative rotation may be deliberately created in the course oftightening the nut for the sake of creating sliding action at the metalinterfaces. The relative rotation, of course, promotes the effectivenessof the seal, as heretofore explained.

Our description in specific detail of the selected embodiment -of theinvention will suggest various changes, substitutions and otherdepartures from our description, within the spirit and scope of theappended claims.

I claim: 1. A method of forming a static fluid-tight seal at a jointsurface formed from metals of a particular malleability characterized bythe steps of:

abutting against the joint surface a sealing ring formed from a materialhaving a greater malleability than the particular malleablity and formedwith at least one narrow rib to reduce the areas of contact with thejoint surface to an area substantially less than the cross-sectionalarea of the rib in the plane of the rib;

placing the ring under sufficient pressure relative to the joint surfaceto produce a plastic flow of the material of the rib against said jointsurface for a widening of the rib and a transfer of the material of therib to the joint surface without any deformation of the joint surfaceand for the creation of a molecular bond between the rib and the jointsurface and the fusing of the material of the rib with the metal of thejoint surface; and

causing relative concentric rotation between the rib and the jointsurface for a wiping action to promote the transfer of metal from therib to the joint surface.

2. A method of forming a static fluid-tight seal at an annular jointsurface at the juncture of two cooperating parts having a particularmalleability, which parts screw together with relative rotation for thecreation of pressure at the joint surface, characterized by the step ofplacing against the joint surface a sealing ring formed with at leastone narrow annular rib of tapered cross section in abutment with thejoint surface, the sealing ring having a greater malleability than theparticular malleability whereby the concentration of the screw generatedpressure on the restricted area of contact of the rib with the jointsurface causes plastic ow of the rib along the joint surface and wipingaction under pressure by virtue of the relative rotation of the parts atthe joint surface to provide a widening of the rib and a fusion of therib with the joint surface for the creation of a molecular bond betweenthe rib and the joint surface,

References Cited in the le of this patent UNITED STATES PATENTS 906,761White Dec. 15, 1908 1,834,581 Ferrel et al. Dec. l, 1931 1,957,605Lamont May 8, 1934 2,543,963 Gain Mar. 6, 1951 FOREIGN PATENTS 1,130,563France Oct. 1, 1956

1. A METHOD OF FORMING A STATIC FLUID-TIGHT SEAL AT A JOINT SURFACEFORMED FROM METALS OF A PARTICULAR MALLEABILITY CHARACTERIZED BY THESTEPS OF: A BUTTING AGAINST THE JOINT SURFACE A SEALING RING FORMED FROMA MATERIAL HAVING A GREATER MALLEABILITY THAN THE PARTICULARMALLEABILITY AND FORMED WITH AT LEAST ONE NARROW RIB TO REDUCE THE AREASOF CONTACT WITH THE JOINT SURFACE TO AN AREA SUBSTANTIALLY LESS THAN THECROSS-SECTIONAL AREA OF THE RIB IN THE PLANE OF THE RIB; PLACING THERING UNDER SUFFICIENT PRESSURE RELATIVE TO THE JOINT SURFACE TO PRODUCEA PLASTIC FLOW OF THE MATERIAL OF THE RIB AGAINST SAID JOINT SURFACE FORA WIDENING OF THE RIB AND A TRANSFER OF THE MATERIAL OF THE RIB TO THEJOINT SURFACE WITHOUT ANY MATERIAL OF THE RIB JOINT SURFACE AND FOR THECREATION OF A MOLECULAR BOND BETWEEN THE RIB AND THE JOINT SURFACE ANDTHE FUSING OF THE MATERIAL OF THE RIB WITH THE METAL OF THE JOINTSURFACE; AND CAUSING RELATIVE CONCENTRIC ROTATION BETWEEN THE RIB ANDTHE JOINT SURFACE FOR A WIPING ACTION TO PROMOTE THE TRANSFER OF METALFROM THE RIB TO THE JOINT SURFACE.